Safety device for extension ladders



July 4, 1939. H. J. COLBERG ,1

SAFETY DEVICE FOR EXTENSION LADDERS Filed April 21, 19s? ,INVENTOR flew/av :7. C01- aseq.

ATTORNEY6 Patented July 4, 1939 UNITED STATES FATENT OFFICE 8 Claims.

The present invention relates to a safety device and particularly to a safety device for extension ladders.

At present extension ladders are constructed with safety devices which prevent the movable ladder from falling, particularly when weight is on same, these devices generally comprising means on one ladder which engage a rung on the other. An object of the present invention is an added safety device which will prevent the mov able ladder from falling if the hoisting rope breaks or slips and the other safety devices have not gripped, and is engageable at any point on the ladder. A further object is a device of this character which is positive and quick acting. A further object is a device which may be readily added to ladders now in use. A still further object is a device which has few parts, is economical to manufacture and rugged in construction. These and other objects will be apparent from the description herein and the accompanying drawing, in which Fig. 1 is an assembled view of one embodiment of the invention;

Fig. 2 is a view on line 2-2 of Fig. 1;

Fig. 3 is a view on line 3-3 of Fig. 2; and

Fig. 4 is a fragmentary view illustrating part of the assembly.

Referring to the drawing, 5 designates a stationary ladder having uprights 6 and rungs l, and 8 designates a movable ladder having uprights 9 and rungs I0. As is usual in ladders of this type, ladder 8 partially nests between the uprights of ladder 5 and rides over the rungs 6 in being hoisted or lowered. A pair of guide members I I secured to ladder 5 extend outwardly and then parallel to the uprights 9 of ladder 8, and a pair of guide members ll secured to ladder 3 extend inwardly and then parallel to uprights E of ladder 5, these guides keeping the ladders in alinement and engagement and also allowing a slight clearance between the rungs 1 of ladder 5 and the uprights 9 of ladder 8.

In accordance with the present invention the top rung of ladder 5 is replaced with a safety device comprising a cross member or shaft l2 which is secured against turning as at M. Carried by and rotatable on shaft I 2 is a sleeve l5, the outer periphery of sleeve l5 being oifset at each end for a distance at least the width of risers 9 to form cam stops 16, the faces I! of the cam stops being scored to assure a better grip. The peripheral offset is such that the radii from the center of shaft [2 to face I! of cam stop It is greater than the radii of a rung plus the clearance between ladders. Sleeve I5 also carries a pulley arm or support l8 located about diametrically opposite cam stops I6 and midway between the ends of sleeve I5, the arm 13 carrying a pulley [9 through which hoisting line 29 passes, one end of the line being secured to the lower rung of ladder 8 and the other end being free for hoisting.

As indicated in dotted lines (Fig. 3), when line 20 is placed under tension the pull on the pulley arm IB tends to rotate sleeve i5 clockwise, moving cam stops l6 out of engagement with the risers 9 of ladder 8. There is provided a stop pin 23 carried by shaft l2 to limit the rotation of sleeve I4 so it will not rotate to dead center, this pin projecting out of an opening 27 cut in sleeve I5, which opening may be enlarged as shown to lighten the weight of the device, the rotation of sleeve l5 being limited by wall 25 of the opening abutting pin 23. However, if line 20 parts or slips, releasing the pull on arm I8 the weight of cams l6 and the frictional engagement of risers 9 with the scored faces ll of cams IE will cause the cams and sleeve I5 to rotate counter-clockwise and jam risers 9 against guides II and prevent ladder 8 from falling. In order to obtain the greatest holding force, guides H are preferably located closely adjacent the safety device.

The safety device is made quick-acting by providing a pair of oppositely wound springs 36 which are housed within sleeve IS on a reduced portion 31 of shaft l2. One end of the spring is caught in a slot 39 on the raised center portion 49 of shaft l2 and retained in same by sleeve l5. The other end 4| of spring 36 projects out of opening 21 of sleeve l5 and abuts wall 25 thereof, tending to rotate the sleeve counterclockwise (Fig. 3). The springs 36 normally act to hold the stops 1 6 in position to jam the ladder and assure quick return to this position upon release of line 26. The shaft I2 is preferably made with a high central portion 40 and reduced end portions 31 to permit springs 36 to be slipped into position. The springs are held in place by bushings 42 which fit over shaft parts 3'! and have the same outside diameter as shaft part 49. Thus assembled shaft l2 may be slipped into sleeve l5, whereupon end 4| of spring 36 is raised through opening 21 and hooked over the sleeve wall end 25. The bushings 42 and shaft 1 l2 have alined holes permitting their being secured as at M against rotation in riser 5. When secured, sleeve l5 may then be rotated counterclockwise (Fig. 3), to tension the springs 36 and when tensioned stop pin 23 may be inserted to prevent unwinding, or the sleeve may be held in wound position until the ladders are assembled, whereupon cam l6 will normally abut riser 9.

The device although shown as being adaptable to extension ladders may be used on other devices of like nature wherein one member is movable relative to another. Although the embodiment shown is preferred because of its simplicity, it is understood that the invention contemplates generally a device wherein a sleeve carrying stop members which normally tend to adjust themselves to stop positions by rotation in one direction and provided with means whereby the sleeve may be manually or mechanically rotated to a release position. With such modifications and equivalent structures contemplated, and with the preferred embodiment shown, the following is claimed:

1. In an extension ladder having a movable part and a stationary part, a safety device comprising a shaft carried by the stationary part, a sleeve mounted on the shaft, cams carried integral with said sleeeve, means normally biasing said sleeve and cams in a direction to cause said cams to engage the rung abutting faces of the risers of the movable ladder part, and manually controlled means for overcoming said bias to rotate the sleeve in the other direction and lift the movable part.

2. In an extension ladder including a stationary ladder and a movable ladder, a safety device comprising a shaft carried by the stationary ladder, a sleeve rotatably mounted on the shaft, stop means on the sleeve normally engaging the rung abutting faces of the risers of the movable ladder, a pulley arm, a pulley carried on the arm, a line secured to the moving ladder and passing through the pulley, said pulley arm being so positioned that when tension is placed on said line said stop means will be rotated to release position, and means adapted upon release of the line tension to move said stop means into abutting engagement with said risers at any set position.

3. In an extension ladder including a stationary ladder and a movable ladder a shaft carried by the stationary ladder, a sleeve rotatably mounted on the shaft, a cam stop on the sleeve adapted to engage the rung abutting faces of the risers of the movable ladder, spring means normally tending to rotate the sleeve and stop to engag ing position, a pulley arm carried by said sleeve, a pulley carried on the arm, a line secured to the movable ladder and passing through the pulley, said pulley arm being so positioned that when tension is placed on said line said stop will be rotated to a release position.

4. A safety device comprising a shaft, said shaft having reduced portions intermediate the end and center enlarged portions, and having slots formed in the center portion, a sleeve adapted to fit over said shaft, said sleeve having openings therein, springs housed in said sleeve on the reduced portion of said shaft, one end of the spring being receivable in the center portion slots and the other projecting through the openings in the sleeve to tend to rotate same in one direction, stop means carried on said sleeve and adapted to be moved to stop position by said springs and release means carried by said sleeve and so positioned relative to the stop means to move same to release position when force is exerted thereon.

5. A safety device as claimed in claim 4 wherein the enlarged end portions of the shaft comprise removable bushings.

6. In a ladder having a movable part and a stationary part, guide means carried by the stationary part, said movable part being nested between the guide means and the rungs of the stationary part, a rotatable rung in the stationary part, stop means carried by said rung and adapted to normally engage the rung-abutting faces of the risers of the movable part at a point above the horizontal axis of the rotatable rung, a rope guide carried by said rung, and a hoisting rope connected to the movable part and passing through said guide and adapted when placed under tension to rotate said rung to move said stop means out of engagement with the risers and lift said movable part.

7. In a ladder having a movable part and a stationary part, guide means carried by the stationary part, said movable part being nested between the guide means and the rungs of the stationary part, a rotatable rung in the stationary part, stop means carried by said rung and adapted to normally engage the rung-abutting inner faces of the risers of the movable part at a point above the horizontal axis of the rotatable rung, a rope guide carried by said rung, a hoisting rope connected to the movable part and passing through said guide and adapted when placed under tension to rotate said rung to move said stop means out of engagement with the risers and lift said movable part, and spring means adapted to rotate said stop means into engagement with the uprights when tension on the rope is released and secure said movable part in any set position.

8. In a ladder having a movable part and a stationary part, guide means carried by the stationary part, said movable part being nested between the guide means and the stationary part with a slight clearance therebetween, a rotatable rung in the stationary part, said rung being provided with peripheral offsets adapted to engage the inner faces of the risers of the movable part, the radius from the center of the rung to the face of the offset being greater than the radius of the rung plus the clearance between the ladders, whereby said ofifsets will normally force said movable part against said guide means; a rope guide carried by said rung, and a hoisting connected to the movable part and passing through said guide and adapted when placed under tension to rotate said rung to move said offsets out of engagement with the risers, whereby said movable part be lifted.

HENRY J. COLBERG. 

